1. The Field of the Invention
The present invention relates to projectiles and, more specifically, projectiles including a non-discarding sabot for discharge from a rifled barrel.
2. Present State of the Art
Guns, such as hand guns and rifles, are designed to interact with a cartridge for discharging a projectile, commonly referred to as a bullet. A cartridge includes a metal case which houses a charge such as gun powder. Mounted at one end of the case is a primer. The projectile is crimped or otherwise secured to the opposing end of the case.
During operation, the cartridge is positioned within the chamber of a gun. By depressing a trigger, a hammer strikes against the primer. In turn, the primer ignites the gun powder which burns at an extremely fast and almost instantaneous rate. As the gunpowder burns, it produces a gas. The rapid expansion of the gas detaches the projectile from the case and pushes the projectile down and out the end of the barrel.
It has long been known that imparting an axial rotation to the projectile significantly improves the accuracy in which the projectile can be fired. Several approaches have been used to impart rotation to the projectile. The most common approach is to form a series of spiral grooves that longitudinally extend along the interior surface of the barrel. The projectile is configured to engage the grooves and thus rotate as the projectile travels the length of the barrel. Momentum allows the projectile to continue to spin after the projectile leaves the barrel.
Depending on the type of projectile used, different approaches have been used to engage the projectile and the grooves. For example, some projectiles are made from relatively soft lead alloys. During discharge, the force of the expanding gas causes the projectile to obterate and radially expand, thereby engaging the grooves. Where the projectile is made of a harder material, the projectile is configured having a diameter slightly larger than the inner diameter of the barrel. As a result, the projectile is forced into the grooves as the projectile travels within the barrel.
Although the operation of guns has become a refined science, there are still several shortcomings associated with conventional projectiles. For example, extended firing of a gun, such as commonly encountered in the military, results in pressure from the expanding gases wearing or deteriorating the interior surface of the gun barrel. Significant wear on the barrel occurs much earlier when hard projectiles are used. The resulting wear on the barrel can produce irregular flight paths in the projectile and can reduce the speed and distance which the projectile travels. In such cases, it is necessary to replace the gun or at least the barrel thereof.
The problem with using lead alloy bullets is that they produce lead build-up on the interior surface of the barrel. Lead build-up increases the resistance on the projectile and can radically increase pressures as well as offset the flight path of the projectile. One approach to solving this problem has been to use various cleaning materials to remove the lead build-up from the interior surface of the barrel. This cleaning process, however, requires the use of toxic solvents that produce a harmful lead waste.
Discarding sabots have been used as another approach to overcoming some of the above problems. A discarding sabot is simply a plastic jacket that is placed over the projectile. During firing, the expanding gas results in expansion of the projectile and sabot such that the sabot, rather than the projectile, engages the grooves of the barrel. By engaging the grooves, the sabot rotates which in turn imparts a rotational movement to the projectile. As the projectile exits the barrel, the sabot is caught by the surrounding air and peeled off of the projectile, allowing the projectile to freely travel. The discarding sabot thus eliminates and prevents the need for the metal projectile to engage the interior surface of the barrel. As a result, wear on the barrel is minimized. Furthermore, there is no metal fouling or buildup in the barrel.
Although sabots produce some advantages, conventional discarding sabots also produce significant problems. For example, as a discarding sabot leaves the barrel, it rapidly expands to release the projectile. In some instances, the sabot breaks apart resulting in a fouled bore. The discarding sabot can produce bore fouling. Specifically, the discarding sabot can clog or otherwise obstruct such systems as sound suppressors, flash suppressors, gas recoil systems, recoil reduction systems, and bore evacuators. Furthermore, if the sabot does not evenly release the projectile, the projectile can become imbalanced and subsequently tumble.